The invention is particularly applicable to so-called structural engines, as used in agricultural tractors. Instead of being supported on mounts on a vehicle body, a structural engine, together with its transmission train, forms the unsprung mass or chassis of the vehicle. For this reason, its engine block needs to be designed to provide strength and rigidity.
The rear end of an engine block commonly has a flange that projects laterally and is used to support ancillary units, such as a fuel and a hydraulic pump to be driven by the crankshaft. The ancillary unit mates with the forward facing surface of the lateral flange and this surface must therefore be machined accurately after the engine block has been cast. In a structural engine, for additional strength, the block has laterally projecting ribs that are joined to the lateral flange on which the ancillary unit is mounted and these ribs interfere with the machining of the forward facing surface of the flange.